The past 100 years have seen a drastic reversal in global temperature trends when compared with historical temperature data.
Research has revealed that the warming trends of the last 100 years have been at odds with the cooling trends that preceded them for over a millennium. Even taking into account natural variations, temperature reconstructions from the last 2000 years have shown that the large spike in warming is not a part of a natural temperature cycle and in fact directly coincides with the expansion of human activity.
Particularly telling were comparisons to earlier temperature trends, such as the Little Ice Age or the Medieval Warm Period. While these trends were localised, the current warming trend is a global phenomenon, and therefore unlike any seen in the past 2000 years.Read more at UNSW